Abstract: Apparatus and methods for non-invasively determining the cardiac output or pulmonary capillary blood flow of a patient using partial re-breathing techniques. The apparatus includes a substantially instantaneously adjustable deadspace volume for accommodating differences in sizes or breathing capacities of various patients. The apparatus may be constructed of inexpensive elements, including one or more two-way valves, which render the apparatus very simple to use and inexpensive so that the unit may be employed as a disposable product. The method of the invention includes estimating the cardiac output or pulmonary capillary blood flow of a patient based on partial pressure of alveolar CO2, rather than on the partial pressure of end tidal CO2, as previously practiced. A computer program for calculating the cardiac output or pulmonary capillary blood flow of a patient is also disclosed.

Abstract: Apparatus and methods for non-invasively determining the cardiac output or pulmonary capillary blood flow of a patient using partial re-breathing techniques. The apparatus includes a substantially instantaneously adjustable deadspace volume for accommodating differences in sizes or breathing capacities of various patients. The apparatus may be constructed of inexpensive elements, including one or more two-way valves, which render the apparatus very simple to use and inexpensive so that the unit may be employed as a disposable product. The method of the invention includes estimating the cardiac output or pulmonary capillary blood flow of a patient based on partial pressure of alveolar CO2, rather than on the partial pressure of end tidal CO2, as previously practiced. A computer program for calculating the cardiac output or pulmonary capillary blood flow of a patient is also disclosed.

Abstract: A re-breathing apparatus including a novel dual chamber reservoir connected to a ventilator circuit by means of a diverting adapter. The dual chamber reservoir utilizes two gas chambers which can be operated in reciprocating fashion. To accomplish re-breathing, expired gas is drawn into one chamber, while gas is ejected from the other chamber. The expired gas is then ejected into the breathing circuit as the patient inspires, while a charge of fresh gas is drawn into the other chamber. The diverting adaptor minimizes mixing of gases being drawn into and ejected from the two chambers. An advantage of the inventive method is that the total volume of gases in the system can be kept constant throughout re-breathing. The preferred embodiment of the inventive reservoir is a one-piece, blow-molded plastic, bellows-like structure which can be manufactured simply and inexpensively for one-time (disposable) use. Actuation of the system may be performed under microprocessor control.

Abstract: Apparatus or systems which employ luminescence-quenching to produce a signal indicative of oxygen concentration.

Abstract: Apparatus or systems which employ luminescence quenching to produce a signal indicative of oxygen concentration. Components of such systems include: an airway adapter, sampling cell, or the like, having a sensor which is excited into luminescence with the luminescence decaying in a manner reflecting the concentration of oxygen in gases flowing through the airway adapter or other flow device; a transducer which has a light source for exciting a luminescable composition in the sensor into luminescence and a light sensitive detector for converting energy emitted from the luminescing composition as that composition is quenched into an electrical signal indicative of oxygen concentration in the gases being monitored; and subsystems for maintaining the sensor temperature constant and for processing the signal generated by the light sensitive detector.

Abstract: A method for removing motion artifacts from devices for sensing bodily parameters and apparatus and system for effecting same. The method includes analyzing segments of measured data representing bodily parameters and possibly noise from motion artifacts. Each segment of measured data may correspond to a single light signal transmitted and detected after transmission or reflection through bodily tissue. Each data segment is frequency analyzed to determine up to three candidate peaks for further analysis. Each of the up to three candidate frequencies may be filtered and various parameters associated with each of the up to three candidate frequencies are calculated. The best frequency, if one exists, is determined by arbitrating the candidate frequencies using the calculated parameters according to predefined criteria. If a best frequency is found, a pulse rate and SpO2 may be output. If a best frequency is not found, other, conventional techniques for calculating pulse rate and Spo2 may be used.

Abstract: A method for removing motion artifacts from devices for sensing bodily parameters and apparatus and system for effecting same. The method includes analyzing segments of measured data representing bodily parameters and possibly noise from motion artifacts. Each segment of measured data may correspond to a single light signal transmitted and detected after transmission or reflection through bodily tissue. Each data segment is frequency analyzed to determine dominant frequency components. The frequency component which represents at least one bodily parameter of interest is selected for further processing. The segment of data is subdivided into subsegments, each subsegment representing one heartbeat. The subsegments are used to calculate a modified average pulse as a candidate output pulse.

Abstract: Apparatus or systems which employ luminescence quenching to produce an oxygen concentration indicative signal. Components of such systems include: (1) an airway adapter, sampling cell, or the like having a sensor which is excited into luminescence with the luminescence decaying in a manner reflecting the concentration of oxygen in gases flowing through the airway adapter or other flow device; (2) a transducer which has a light source for exciting a luminescable composition in the sensor into luminescence and a light sensitive detector for converting energy emitted from the luminescing composition as that composition is quenched into an electrical signal indicative of oxygen concentration in the gases being monitored; and (3) subsystems for maintaining the sensor temperature constant and for processing the signal generated by the light sensitive detector. Sensors for systems of the character just described, methods of fabricating those sensors, and methods for installing the sensors in the flow device.

Abstract: A method of non-invasively estimating the intrapulmonary shunt in a patient. The method includes non-invasively measuring respiratory flow, respiratory carbon dioxide content, and arterial blood oxygen content. A re-breathing process is employed to facilitate an estimate of the patient's pulmonary capillary blood flow. Any inaccuracies of the arterial blood oxygen content are corrected to provide a substantially accurate arterial blood oxygen content measurement. The respiratory flow, carbon dioxide content and arterial blood oxygen content measurements, and the pulmonary capillary blood flow estimate are employed to estimate an intrapulmonary shunt of the patient. The invention also includes a method of determining the total cardiac output of the patient which considers the estimated intrapulmonary shunt.

Abstract: A method of compensating for non-metabolic changes in respiratory or blood gas parameters including generating a compensatory signal based on the magnitude of the non-metabolic change and the amount of time elapsed since the onset of the non-metabolic change. The method of the present invention is useful for compensating for non-metabolic changes in non-invasive carbon dioxide elimination measurements and, particularly, when carbon dioxide elimination is employed to determine cardiac output on a non-invasive, continuous basis.

Abstract: Apparatus and methods for non-invasively determining the cardiac output or pulmonary capillary blood flow of a patient using partial re-breathing techniques. The apparatus includes a substantially instantaneously adjustable deadspace volume for accommodating differences in sizes or breathing capacities of various patients. The apparatus may be constructed of inexpensive elements, including one or more two-way valves, which render the apparatus very simple to use and inexpensive so that the unit may be employed as a disposable product. The method of the invention includes estimating the cardiac output or pulmonary capillary blood flow of a patient based on partial pressure of alveolar CO2 rather than on the partial pressure of end tidal CO2, as previously practiced. A computer program for calculating the cardiac output or pulmonary capillary blood flow of a patient is also disclosed.

Abstract: A method of continuously, non-invasively determining the cardiac output of a patient. The method includes intermittently measuring the cardiac output, the volume of carbon dioxide exhaled by the patient per breath, and determining the arterial-venous gradient of the patient or a similar substantially constant value by dividing the volume of carbon dioxide exhaled by the measured cardiac output. The arterial-venous gradient or similar substantially constant value may then be employed to determine the cardiac output of the patient on a breath-by-breath basis. The carbon dioxide elimination, which is non-invasively measured as the volume of carbon dioxide exhaled by the patient per breath, is divided by the arterial-venous gradient or the substantially constant value to determine the cardiac output.

Abstract: A re-breathing method for determining pulmonary capillary blood flow that accounts for changes in the carbon dioxide content of a patient. The carbon dioxide elimination and partial pressure of end tidal carbon dioxide of the patient are measured prior to re-breathing, during re-breathing, and after re-breathing. A rate of change of carbon dioxide content of the venous blood of the patient is then calculated. The rate of change is then employed in calculating the pulmonary capillary blood flow of the patient.

Abstract: A method of sampling one or more respiratory profile characteristics and monitoring a variety of respiratory profile parameters. The sampled respiratory characteristics include respiratory flow rate, respiratory pressure, and partial pressure of at least one constituent of a patient's respiration. The method detects patient breaths, determines whether each breath, is a spontaneous breath or a ventilator-induced breath, and calculates various respiratory profile parameters based on the sampled measurements. The method displays the respiratory profile parameters in graphic and numeric forms. Preferably, the method allows a user to select the displayed respiratory profile parameters.

Abstract: An airway valve, method of operation and ventilator circuit including the valve. The airway valve includes an outer housing defining a primary passage including first and second coaxial primary passage portions mutually directly communicating within the housing, and first and second diversion passages extending transversely to the primary passage, each diversion passage being integral with the housing and opening onto a primary passage portion. The airway valve controls diversion of air flow between the first primary passage portion and the second primary passage portion into and through an enlarged volume defined by a re-breathing loop external to the housing via the first and second diversion passages. To selectively effect such diversion, an elliptical valve element is oriented within the housing at a 45.degree. angle to both the first primary passage portion and the first diversion passage and disposed on the end of an actuation shaft aligned with the first diversion passage.

Abstract: An airway valve for re-breathing, a ventilator circuit including same and a method of operating the airway valve. The airway valve includes a housing having first and second primary passages extending through the wall thereof and mutually directly communicating within the housing through a spring-biased valve assembly in the form of first and second diaphragms respectively and simultaneously movable in tandem within the housing into and out of contact with first and second valve seats on a valve body with which the first primary passage communicates. The valve assembly also controls diversion of air flow between the first primary passage and the second primary passage into and through an enlarged volume defined by a re-breathing loop external to the housing via first and second diversion passages, which also extend through the wall of the housing.

Abstract: An oximetry sensor comprising a foam wrap member including a fastener, back film mounting member, LED assembly and photodiode connected to a cable, support rings for the LED assembly and photodiode, window film for the LED assembly and photodiode, and a top liner.

Abstract: A non-invasive system and procedure for deriving the blood gas content for a patient. The system measures the carbon dioxide concentration of the expiratory breath relative to volume. This data is then processed to derive arterial blood gas levels of carbon dioxide. If data sampling is in the time domain, the processing shifts the data from the time domain to the volume domain. The processing also iteratively assesses the significance of numerous variables. The resulting relationship provides a fast and accurate measure of blood gas content for both healthy and diseased lung patients.

Abstract: Sampling attachments or systems for infrared gas analyzers of the non-dispersive type. Major components of the system include a sampling device or cuvette, a vacuum pump for effecting a flow of the gases to be analyzed through the cuvette, a microprocessor based pump control, and a switch which is closed and allows the pump to be turned on only if an appropriate sampling cuvette is connected up to the pump. The sampling attachments are designed for medical applications--to provide readings of tidal carbon dioxide, for example. They have a minimally invasive nasal cannula for collecting the gases which are to be subjected to analysis; viz., those exhaled by a patient. These gases are conducted to the cuvette through a line which is gastight but allows moisture to escape, thereby keeping moisture mixed with the gases being analyzed from corrupting the readings outputted by the gas analyzer.